Sometimes we want to do more than
summarize a bunch of scores. Sometimes we want to talk about particular scores
within the bunch. We may want to tell other people about whether or not a score
is above or below average. We may want to tell other people how far away a
particular score is from average. We might also want to compare scores from
different bunches of data. We will want to know which score is better. Z-scores
can help with all of this.

Z-Scores tell us whether a particular
score is equal to the mean, below the mean or above the mean of a bunch of
scores. They can also tell us how far a particular score is away from the mean.
Is a particular score close to the mean or far away?

How typical a particular score is within
bunch of scores. If data are normally distributed, approximately 95% of the data
should have Z-score between -2 and +2. Z-scores that do not fall within this
range may be less typical of the data in a bunch of scores.